The present invention relates to a method of producing a semiconductor element. More specifically, the present invention relates to a method of producing a semiconductor element, in which a contact hole is formed in an interlayer insulation layer formed of more than three layers of films such as a phosphorus-containing silicon oxide film (a PSG film), a silicon nitride film (an SiN film) and an insulation film.
Conventionally, when a semiconductor element is produced, first, an interlayer insulation layer having a three-layer structure is formed on a wiring portion layer. Then, a contact hole is formed in the interlayer insulation layer through an etching process (refer to Patent References 1 and 2).    Patent Reference 1: Japanese Patent Publication No. 07-94441    Patent Reference 2: Japanese Patent Publication No. 05-343347
In particular, when the contact hole is formed in the interlayer insulation layer having the three-layer structure formed of a phosphorus-containing silicon oxide film (a PSG film), a silicon nitride film (an SiN film) and an insulation film (for example, an NSG film), the following manufacturing steps are generally performed.
In the first step, a mask pattern for forming the contact hole is formed on the PSG film through a photolithography technology. In the second step, a contact hole forming area of the PSG film is removed through a wet etching process. In the third step, a contact hole forming area of the SiN film and the insulation film (for example, an NSG film) is removed through an anisotropic dry etching process. In the fourth step, the mask pattern is removed through an asking technology.
In the conventional method including the manufacturing steps described above, it is difficult to prevent a residue with a column shape from generating in the anisotropic dry etching process or the wet etching process.
In view of the problems described above, an object of the present invention is to provide a method of producing a semiconductor element capable of solving the problems of the conventional method of producing the semiconductor element, and preventing a residue with a column shape from generating in an etching process.
Further objects and advantages of the invention will be apparent from the following description of the invention.